/*
 * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Development of this code funded by Astaro AG (http://www.astaro.com/)
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/log2.h>
#include <linux/jhash.h>
#include <linux/netlink.h>
#include <linux/workqueue.h>
#include <linux/rhashtable.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>

/* We target a hash table size of 4, element hint is 75% of final size */
#define NFT_HASH_ELEMENT_HINT 3

struct nft_hash {
	struct rhashtable		ht;
	struct delayed_work		gc_work;
};

struct nft_hash_elem {
	struct rhash_head		node;
	struct nft_set_ext		ext;
};

struct nft_hash_cmp_arg {
	const struct nft_set		*set;
	const u32			*key;
	u8				genmask;
};

static const struct rhashtable_params nft_hash_params;

static inline u32 nft_hash_key(const void *data, u32 len, u32 seed)
{
	const struct nft_hash_cmp_arg *arg = data;

	return jhash(arg->key, len, seed);
}

static inline u32 nft_hash_obj(const void *data, u32 len, u32 seed)
{
	const struct nft_hash_elem *he = data;

	return jhash(nft_set_ext_key(&he->ext), len, seed);
}

static inline int nft_hash_cmp(struct rhashtable_compare_arg *arg,
			       const void *ptr)
{
	const struct nft_hash_cmp_arg *x = arg->key;
	const struct nft_hash_elem *he = ptr;

	if (memcmp(nft_set_ext_key(&he->ext), x->key, x->set->klen))
		return 1;
	if (nft_set_elem_expired(&he->ext))
		return 1;
	if (!nft_set_elem_active(&he->ext, x->genmask))
		return 1;
	return 0;
}

static bool nft_hash_lookup(const struct net *net, const struct nft_set *set,
			    const u32 *key, const struct nft_set_ext **ext)
{
	struct nft_hash *priv = nft_set_priv(set);
	const struct nft_hash_elem *he;
	struct nft_hash_cmp_arg arg = {
		.genmask = nft_genmask_cur(net),
		.set	 = set,
		.key	 = key,
	};

	he = rhashtable_lookup_fast(&priv->ht, &arg, nft_hash_params);
	if (he != NULL)
		*ext = &he->ext;

	return !!he;
}

static bool nft_hash_update(struct nft_set *set, const u32 *key,
			    void *(*new)(struct nft_set *,
					 const struct nft_expr *,
					 struct nft_regs *regs),
			    const struct nft_expr *expr,
			    struct nft_regs *regs,
			    const struct nft_set_ext **ext)
{
	struct nft_hash *priv = nft_set_priv(set);
	struct nft_hash_elem *he, *prev;
	struct nft_hash_cmp_arg arg = {
		.genmask = NFT_GENMASK_ANY,
		.set	 = set,
		.key	 = key,
	};

	he = rhashtable_lookup_fast(&priv->ht, &arg, nft_hash_params);
	if (he != NULL)
		goto out;

	he = new(set, expr, regs);
	if (he == NULL)
		goto err1;

	prev = rhashtable_lookup_get_insert_key(&priv->ht, &arg, &he->node,
						nft_hash_params);
	if (IS_ERR(prev))
		goto err2;

	/* Another cpu may race to insert the element with the same key */
	if (prev) {
		nft_set_elem_destroy(set, he, true);
		atomic_dec(&set->nelems);
		he = prev;
	}

out:
	*ext = &he->ext;
	return true;

err2:
	nft_set_elem_destroy(set, he, true);
	atomic_dec(&set->nelems);
err1:
	return false;
}

static int nft_hash_insert(const struct net *net, const struct nft_set *set,
			   const struct nft_set_elem *elem,
			   struct nft_set_ext **ext)
{
	struct nft_hash *priv = nft_set_priv(set);
	struct nft_hash_elem *he = elem->priv;
	struct nft_hash_cmp_arg arg = {
		.genmask = nft_genmask_next(net),
		.set	 = set,
		.key	 = elem->key.val.data,
	};
	struct nft_hash_elem *prev;

	prev = rhashtable_lookup_get_insert_key(&priv->ht, &arg, &he->node,
					       nft_hash_params);
	if (IS_ERR(prev))
		return PTR_ERR(prev);
	if (prev) {
		*ext = &prev->ext;
		return -EEXIST;
	}
	return 0;
}

static void nft_hash_activate(const struct net *net, const struct nft_set *set,
			      const struct nft_set_elem *elem)
{
	struct nft_hash_elem *he = elem->priv;

	nft_set_elem_change_active(net, set, &he->ext);
	nft_set_elem_clear_busy(&he->ext);
}

static void *nft_hash_deactivate(const struct net *net,
				 const struct nft_set *set,
				 const struct nft_set_elem *elem)
{
	struct nft_hash *priv = nft_set_priv(set);
	struct nft_hash_elem *he;
	struct nft_hash_cmp_arg arg = {
		.genmask = nft_genmask_next(net),
		.set	 = set,
		.key	 = elem->key.val.data,
	};

	rcu_read_lock();
	he = rhashtable_lookup_fast(&priv->ht, &arg, nft_hash_params);
	if (he != NULL) {
		if (!nft_set_elem_mark_busy(&he->ext) ||
		    !nft_is_active(net, &he->ext))
			nft_set_elem_change_active(net, set, &he->ext);
		else
			he = NULL;
	}
	rcu_read_unlock();

	return he;
}

static void nft_hash_remove(const struct nft_set *set,
			    const struct nft_set_elem *elem)
{
	struct nft_hash *priv = nft_set_priv(set);
	struct nft_hash_elem *he = elem->priv;

	rhashtable_remove_fast(&priv->ht, &he->node, nft_hash_params);
}

static void nft_hash_walk(const struct nft_ctx *ctx, const struct nft_set *set,
			  struct nft_set_iter *iter)
{
	struct nft_hash *priv = nft_set_priv(set);
	struct nft_hash_elem *he;
	struct rhashtable_iter hti;
	struct nft_set_elem elem;
	int err;

	err = rhashtable_walk_init(&priv->ht, &hti, GFP_KERNEL);
	iter->err = err;
	if (err)
		return;

	err = rhashtable_walk_start(&hti);
	if (err && err != -EAGAIN) {
		iter->err = err;
		goto out;
	}

	while ((he = rhashtable_walk_next(&hti))) {
		if (IS_ERR(he)) {
			err = PTR_ERR(he);
			if (err != -EAGAIN) {
				iter->err = err;
				goto out;
			}

			continue;
		}

		if (iter->count < iter->skip)
			goto cont;
		if (nft_set_elem_expired(&he->ext))
			goto cont;
		if (!nft_set_elem_active(&he->ext, iter->genmask))
			goto cont;

		elem.priv = he;

		iter->err = iter->fn(ctx, set, iter, &elem);
		if (iter->err < 0)
			goto out;

cont:
		iter->count++;
	}

out:
	rhashtable_walk_stop(&hti);
	rhashtable_walk_exit(&hti);
}

static void nft_hash_gc(struct work_struct *work)
{
	struct nft_set *set;
	struct nft_hash_elem *he;
	struct nft_hash *priv;
	struct nft_set_gc_batch *gcb = NULL;
	struct rhashtable_iter hti;
	int err;

	priv = container_of(work, struct nft_hash, gc_work.work);
	set  = nft_set_container_of(priv);

	err = rhashtable_walk_init(&priv->ht, &hti, GFP_KERNEL);
	if (err)
		goto schedule;

	err = rhashtable_walk_start(&hti);
	if (err && err != -EAGAIN)
		goto out;

	while ((he = rhashtable_walk_next(&hti))) {
		if (IS_ERR(he)) {
			if (PTR_ERR(he) != -EAGAIN)
				goto out;
			continue;
		}

		if (!nft_set_elem_expired(&he->ext))
			continue;
		if (nft_set_elem_mark_busy(&he->ext))
			continue;

		gcb = nft_set_gc_batch_check(set, gcb, GFP_ATOMIC);
		if (gcb == NULL)
			goto out;
		rhashtable_remove_fast(&priv->ht, &he->node, nft_hash_params);
		atomic_dec(&set->nelems);
		nft_set_gc_batch_add(gcb, he);
	}
out:
	rhashtable_walk_stop(&hti);
	rhashtable_walk_exit(&hti);

	nft_set_gc_batch_complete(gcb);
schedule:
	queue_delayed_work(system_power_efficient_wq, &priv->gc_work,
			   nft_set_gc_interval(set));
}

static unsigned int nft_hash_privsize(const struct nlattr * const nla[])
{
	return sizeof(struct nft_hash);
}

static const struct rhashtable_params nft_hash_params = {
	.head_offset		= offsetof(struct nft_hash_elem, node),
	.hashfn			= nft_hash_key,
	.obj_hashfn		= nft_hash_obj,
	.obj_cmpfn		= nft_hash_cmp,
	.automatic_shrinking	= true,
};

static int nft_hash_init(const struct nft_set *set,
			 const struct nft_set_desc *desc,
			 const struct nlattr * const tb[])
{
	struct nft_hash *priv = nft_set_priv(set);
	struct rhashtable_params params = nft_hash_params;
	int err;

	params.nelem_hint = desc->size ?: NFT_HASH_ELEMENT_HINT;
	params.key_len	  = set->klen;

	err = rhashtable_init(&priv->ht, &params);
	if (err < 0)
		return err;

	INIT_DEFERRABLE_WORK(&priv->gc_work, nft_hash_gc);
	if (set->flags & NFT_SET_TIMEOUT)
		queue_delayed_work(system_power_efficient_wq, &priv->gc_work,
				   nft_set_gc_interval(set));
	return 0;
}

static void nft_hash_elem_destroy(void *ptr, void *arg)
{
	nft_set_elem_destroy((const struct nft_set *)arg, ptr, true);
}

static void nft_hash_destroy(const struct nft_set *set)
{
	struct nft_hash *priv = nft_set_priv(set);

	cancel_delayed_work_sync(&priv->gc_work);
	rhashtable_free_and_destroy(&priv->ht, nft_hash_elem_destroy,
				    (void *)set);
}

static bool nft_hash_estimate(const struct nft_set_desc *desc, u32 features,
			      struct nft_set_estimate *est)
{
	unsigned int esize;

	esize = sizeof(struct nft_hash_elem);
	if (desc->size) {
		est->size = sizeof(struct nft_hash) +
			    roundup_pow_of_two(desc->size * 4 / 3) *
			    sizeof(struct nft_hash_elem *) +
			    desc->size * esize;
	} else {
		/* Resizing happens when the load drops below 30% or goes
		 * above 75%. The average of 52.5% load (approximated by 50%)
		 * is used for the size estimation of the hash buckets,
		 * meaning we calculate two buckets per element.
		 */
		est->size = esize + 2 * sizeof(struct nft_hash_elem *);
	}

	est->class = NFT_SET_CLASS_O_1;

	return true;
}

static struct nft_set_ops nft_hash_ops __read_mostly = {
	.privsize       = nft_hash_privsize,
	.elemsize	= offsetof(struct nft_hash_elem, ext),
	.estimate	= nft_hash_estimate,
	.init		= nft_hash_init,
	.destroy	= nft_hash_destroy,
	.insert		= nft_hash_insert,
	.activate	= nft_hash_activate,
	.deactivate	= nft_hash_deactivate,
	.remove		= nft_hash_remove,
	.lookup		= nft_hash_lookup,
	.update		= nft_hash_update,
	.walk		= nft_hash_walk,
	.features	= NFT_SET_MAP | NFT_SET_TIMEOUT,
	.owner		= THIS_MODULE,
};

static int __init nft_hash_module_init(void)
{
	return nft_register_set(&nft_hash_ops);
}

static void __exit nft_hash_module_exit(void)
{
	nft_unregister_set(&nft_hash_ops);
}

module_init(nft_hash_module_init);
module_exit(nft_hash_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_ALIAS_NFT_SET();